Vacuum lightning-arrester.



E. T. MAY? VACUUM LIGHTNING ARRESTER.

APPLICATION FILED HOV. 9. 1916.;

1,244,528. Patent-e01 Oct. 30, 1917.

&

WAf/y UNITED STATES PATENT OFFICE.

DAVID T. MAY, OF NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COMPANY,

INCORPORATED,

011 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

VACUUM LIGHTNING-ARBESTER.

Specification of Letters Patent.

Patented Oct. 30, 1917.

- The voltage, at which a spark will be struck between the electrodes of a vacuum lightning arrester, and thus give protection .to the apparatus on the line, is determined I by the distance of separatlon of the electrodes and the degree of vacuum in the arrester. However, when the vacuum is destroyed and the pressure increased to that of the atmosphere, the sparking voltage will be too high for satisfactory protection of the apparatus. It is, therefore, desirable from the standpoint of protection to have means for short-circuiting the arrester, that is, establishing a conducting path of low resistance in parallel to the spark gap, if the evacuated container leaks and allows the pressure within it to increase to that of the atmosphere. A short-circuited arrester can be detected by well-known line tests and a new one put in its place.

The present invention is characterized by the employment of deliquescent material which normally separates short-circuiting contact members which tend to engage one another. When the deliquescent material is softened by absorption of moisture carried into the evacuated container by the air whenthe vacuum fails, it permits the shortcircuiting contact members to engage one another.

The drawing shows a vacuum lightning arrester having the present invention em- .bodied therein, a portion of the container being broken away and certain parts being shown in cross-section.

The vacuum lightmng arrester hereinillustrated of the general type fully described in a United States application forpatent in my name, Serial No. 101,747, filed June 5, 1916, and assigned to the same assignee as the'present case. The arrester comprises an evacuated glass container 1, mounted upon a base 2. Within the container 1 is ahollow. glass stem 3, upon which concentric cylindrical electrodes are supported. Electrical connection with the electrodes is obtained through leading-in wires 4 and 5, which are led from the base 2 through the stem 3 and are connected to the electrodes bymeans of screws 6 and 7.

Secured to the electrodes by screws 6 and 7 are spring members 8 and 9 which are preferably made of flat piecesof brass or other conducting material. These spring members are bent in a manner suitable for holding the short-circuiting device between their upper ends, substantially as shown in the drawing.

The short-circuiting device herein illustrated cOmprises a container consisting of tubes 10 and 11 which are preferably made of some non-conducting material such as glass. Tube 10 has a large bore 12, while {tube 11 has a small bore 13 with an enlarged portion 14, at its inner end. A stationary contact member 15 is carried in tube 11 and projects through the outer end, being connectedta suitable terminal 16, which is cemented to the tube 11 and through which electrical contact is made with the spring member 8. The tube 10 contains a movable lcontact member in the shape of a helical spring 17, oneend of which projects through -,tube 10 and is connected to terminal 18 engaged by the sprin member 9. The other .end of the spring 1? is straight and engages :under compression a disk or pellet of deliquescent material 19 placed in the enlarged portion 14 of tube 11. The tubes are sealed together on the line 20. A small aperture 21 is cut in tube 10 in order that the pressure in .the arrester and within tubes 10 and 11 may always be the same. In order to prevent the deliquescent material from absorbing moisture from the air and thus operating the device between the time of its assembly and the time of exhausting and sealing the arrester, aperture 21 is sealed with a low temperature melting wax 22 such as 'paraflin. This wax can readily be-melted during the exhausting operation, leaving the aperture open. Means is provided for taking up the melted wax, consisting of a piece of slitted blotting paper 23 surrounding the wax and held by spring clips 24. This arrangement not only prevents the melted wax from falling on the parts below, but insures the removal of the wax from the aperture.

As long as the arrestenremains in it;

tending evacuated condition the pellet 19 of delique'scent material will remain hard and will separate the stationary contact member 15 and the movable contact member .17. If, however, the arrester' leaks and permits air to enter, the moisture carried in with the air will soften the pellet 19 and permit it to be pierced by the prolonged end of helical spring 17, which is under compression, thus making electrical contact with contact mem .ber 15 and completing the short circuit between the electrodes.

The description of the invention is herein confined to one form of short-circuiting device for use with a certain construction of vacuum protective device. It will be readily understood, however, that the invention may be embodied in many other forms and used in connection with practically all types of vacuum protective devices.

What is claimed is:

1. In a vacuum lightning arrester, a shortcircuiting device comp rising contact members to engage one another, and means comprising deliquescent material normally retaining said members separated.

2. In a vacuum lightning arrester, a shortcircuitin bers ten ng to engage one another, and deliquescent material normally separating said contact members.

3. In a vacuum lightningarrester, a shortcircuiting device comprising a fixed contact member, a movable contact member tending to engage said fixed member, and de1iquescent material normally preventing said movdevice comprising contact memable contact member from engaging said fixed contact member.

4. In a vacuum lightning arrester, a shortcircuitin device comprising a container of non-con ucting material, a fixed contact member located in one end of said container and projecting therefrom, a movable contact member located in the other end of'said said container and projecting therefrom, a

movable contact member located in the other end of said container and projecting therefrom and tending to engage said fixed contact member, a deliquescent material located between said contact members and normally preventing their engagement, terminals to which said projections of said contact members are connected, and spring metallic members bearing against said terminals and firmly holding said short-circuiting device between their ends, the other ends of said sprin metallic members being connected to the e ectrodes of said vacuum lightning arrester.

In witness whereof, I hereunto subscribe my name this 8th day of November A. D. 1916.

DAVID T. MAY. 

